This invention relates to the provision of telephone services to plain-old-telephone (POT) customer premises equipment, or POT CPE. In the context of this disclosure POT CPE is CPE that does not employ frequency multiplexing or time multiplexing technology that provides a capability to support more than one connection at any one time.
A telephone service provider's “customer line”, which sometimes is referred to simply as the “line,” is a telephone wire-pair that extends from the telephone service provider network to a customer's premises. In contrast a telephone “trunk” spans between two switches of the telephone service provider network, or between a provider's switch and a PBX.
Years ago the use of party lines was quite prevalent. In a party line arrangement, two or more parties that have a different called number connect their telephone instrument to a single customer line. Each party can initiate outgoing phone calls, identically to how different extension phones can initiate outgoing calls. Just as with extension phones, however, the party line arrangement provided no privacy. On the incoming calls side, matters are less simple. Given that party A needs to be reachable by dialing called number N1, and party B needs to be reachable by dialing called number N2, it is important to have a method for providing ringing signal to party A or to party B, but not simultaneously to both, based on whether a caller dialed called number N1 or N2. One way to achieve this takes advantage of the fact that a telephone line consists of two wires, called “tip” and “ring,” neither of which is grounded. By connecting the ringer of party A between “tip” and ground, and the ringer of party B between “ring” and ground, it is possible to select whether the ringer of party A or party B gets activated by applying the ringing signal between either “tip” and ground or “ring” and ground.
Another approach employs coded ringing, where the audible ringing pattern for one party is different from that for other party or parties. This approach allows creating a party line for more than two called numbers. Often, this approach is used in a household where a teenager gets his, or her, own phone number, but a single customer line (wire pair) is extended into the household.
Because of significant reductions in the cost of switching equipment, not to mention the privacy issue, the use of party lines has all but disappeared and, nowadays, almost all customer lines carry telephone traffic that is destined to one called number, except for households that subscribe to “teen ringing.” In “teen ringing” arrangements, the different called numbers that are assigned to a line are alerted with distinctive ringing signal bursts. All extension telephones are subjected to the ringing signal bursts, and users recognize the called number that is being alerted by the different ringing sounds.
Incoming calls, of course, can come from any party whatsoever, and recent advances in telecommunications have recognized that customers may want to have different treatments applied to incoming calls based on the identity of the calling party; e.g., call blocking. To offer customer services based on the calling party's identity the calling party's ID was extended from the switch that originates calls to the switch that terminates calls. To offer customers this information as well, the calling party's ID (typically referred to as “caller ID”) concept was invented and patented in U.S. Pat. No. 4,551,581 by Doughty in November 1985.
In accordance with the Doughty patent, a data message (special service messages) may be sent to an on-hook called station during the silent interval between ringing signals that comprises any number of character bytes, each with additional start and stop bits. The first character of the message identifies the type of message such as, for example, calling/called directory number, special service indicator, personal messages, etc. The second character specifies the number of subsequent character bytes in the message. The next characters represent the digits of the calling station directory number, and the last character sent to the called station is a check sum that the station set uses to verify that errors have not been introduced in transmission. This digital information is communicated through frequency shift keying (FSK) modulation of a carrier.
U.S. Pat. No. 5,544,233 describes an arrangement more than one called number is directed to a single line. The switching apparatus that connects to the line encodes the called number (in Frequency Shift Keying) into the analog signal that is sent to the line and, before the switching apparatus applies ringing to the line, a coverter associated with the telephone demodulates and displays the called number and causes an audible sound, such as distinctive ringing, to be sounded. Action other than sounding a ringing can also be taken, in accordance with the programming within the converter. Illustratively, the converter can include a number of ports that are connected to metering devices such as electric meters and water meters, and be further sensitive to a code appended to the called number, which directs the converter to connect to one of such metering devices and send out telemetry data.